Fructooligosaccharides (FOS) and fructans are short chains of fructose molecules that can cause symptoms due to fermentation.
Fructan / FOS intolerance (more vegetable and grain-related) often overlaps with fructose intolerance (more fruit and sweetener-related), but this is not always the case.
Therefore, separate trial elimination under the guidance of a dietician is advised to minimise unnecessary reduction of these often healthy foods. Food known to contain significant amounts of FOS, such as inulins and fructans, are shown below (>1g/100g). It should be noted that the FOS are generally not sweet and many foods have not been characterized regarding their FOS content. You may well discover differences between sources regarding the amount of FOS in food. This is due to differences in the fruit assessed (ripeness, type) as well as the methods used for quantification. Daily consumption in Western diets varies between 1 and 15g.
|Food||Fructan content (g/100g whole product)|
Data sources for the above table include Muir J et al. Fructan and free fructose content of common Australian vegetables and fruit. J Agric Food Chem 2007;55:6619-6627; Food Standards of Australia and New Zealand tables; L’Homme et al. Evaluation of fructans in various fresh and stewed fruits by high-performance anion-exchange chromatography with pulsed amperometric detection. J Chromatogr A. 2001;22:291-297; van Loo J et al. On the presence of inulin and oligofructose as natural ingredients in the western diet. Crit Rev Food Sci Nutr 1995;35:525-552.
The following vegetables and fruit have higher levels (>0.2g/100g of whole product) of the FOS kestose and nyatose, the significance of which is unproven: asparagus, beetroot, blueberries, broccoli, Brussel sprouts, cabbage, red chili, garlic, radicchio lettuce, longon, nectarines, okra, white onion, snow peas, pineapple, raspberries. However, they may contribute to similar symptoms as the better known fructans. In case the reduction of the better known fructans does not lead to symptom relief, abstinence from these foods may be tried for a limited period to assess their contribution to symptoms.